linux-kernel - Re: [PATCH] soc: imx6qp: Use GENPD_FLAG_ALWAYS

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Date:   Fri, 13 Jul 2018 13:21:55 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Leonard Crestez <leonard.crestez@....com>
Cc:     Shawn Guo <shawnguo@...nel.org>,
        Lucas Stach <l.stach@...gutronix.de>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Fabio Estevam <fabio.estevam@....com>,
        Robin Gong <yibin.gong@....com>,
        Anson Huang <Anson.Huang@....com>,
        Dong Aisheng <aisheng.dong@....com>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>,
        Sascha Hauer <kernel@...gutronix.de>
Subject: Re: [PATCH] soc: imx6qp: Use GENPD_FLAG_ALWAYS_ON for PU errata

On 13 July 2018 at 12:01, Leonard Crestez <leonard.crestez@....com> wrote:
> This is functionally identical but simpler and slightly faster.
>
> The PU domain is turned on at boot time and never turned off. In the
> current implementation the pm core will repeatedly call power_off when
> the domain is unused and get -EBUSY back. If the domain is marked as
> "always on" instead the pm core won't even attempt to turn it off.
>
> In theory on 6qp it is safe to turn PU off in suspend, however that is
> best accomplished with a new core flag.
>
> Signed-off-by: Leonard Crestez <leonard.crestez@....com>

Reviewed-by: Ulf Hansson <ulf.hansson@...aro.org>

Kind regards
Uffe

> ---
>  drivers/soc/imx/gpc.c | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
>
> Previous discussion:
> * https://lkml.org/lkml/2018/7/11/431
> * https://lkml.org/lkml/2018/7/10/103
>
> Attempt at turning PU off in suspend:
> * https://lkml.org/lkml/2018/7/6/698
>
> diff --git a/drivers/soc/imx/gpc.c b/drivers/soc/imx/gpc.c
> index faf13a0b85d6..f31978e5af20 100644
> --- a/drivers/soc/imx/gpc.c
> +++ b/drivers/soc/imx/gpc.c
> @@ -45,11 +45,10 @@ struct imx_pm_domain {
>         struct clk *clk[GPC_CLK_MAX];
>         int num_clks;
>         unsigned int reg_offs;
>         signed char cntr_pdn_bit;
>         unsigned int ipg_rate_mhz;
> -       unsigned int flags;
>  };
>
>  static inline struct imx_pm_domain *
>  to_imx_pm_domain(struct generic_pm_domain *genpd)
>  {
> @@ -60,13 +59,10 @@ static int imx6_pm_domain_power_off(struct generic_pm_domain *genpd)
>  {
>         struct imx_pm_domain *pd = to_imx_pm_domain(genpd);
>         int iso, iso2sw;
>         u32 val;
>
> -       if (pd->flags & PGC_DOMAIN_FLAG_NO_PD)
> -               return -EBUSY;
> -
>         /* Read ISO and ISO2SW power down delays */
>         regmap_read(pd->regmap, pd->reg_offs + GPC_PGC_PUPSCR_OFFS, &val);
>         iso = val & 0x3f;
>         iso2sw = (val >> 8) & 0x3f;
>
> @@ -419,12 +415,12 @@ static int imx_gpc_probe(struct platform_device *pdev)
>                 return ret;
>         }
>
>         /* Disable PU power down in normal operation if ERR009619 is present */
>         if (of_id_data->err009619_present)
> -               imx_gpc_domains[GPC_PGC_DOMAIN_PU].flags |=
> -                               PGC_DOMAIN_FLAG_NO_PD;
> +               imx_gpc_domains[GPC_PGC_DOMAIN_PU].base.flags |=
> +                               GENPD_FLAG_ALWAYS_ON;
>
>         /* Keep DISP always on if ERR006287 is present */
>         if (of_id_data->err006287_present)
>                 imx_gpc_domains[GPC_PGC_DOMAIN_DISPLAY].base.flags |=
>                                 GENPD_FLAG_ALWAYS_ON;
> --
> 2.17.1
>